Can anyone catch Chris Froome?

Tejay Van Garderen, American cycling's big hope for a top three placing in the 2015 Tour de France, found out today just how long the road to Paris still is for all the riders in this year's peloton. The 26 year old was forced out of the Tour by illness midway through the 17th stage.

Van Garderen started the stage from Digne-les-Bains to Pra Loup in third place overall, still talking up his chances of overall victory. An hour into the race however – after attacks from Nairo Quintana of Colombia accelerated the pace – the Montanan was clinging on at the back of the bunch, surrounded by anxious team mates as he slipped behind the leading groups.

The day after a rest day, with the rhythm of racing interrupted by long-winded press conferences and 24 hours without the adrenaline rush of racing, it's often hard to get going again. As Van Garderen today found out. After almost three weeks on the race the motivation to suffer can begin to slip away too.

Van Garderen's Tour ended 70 kilometres from Pra Loup, when, as they say, he had been 'pedalling squares' for far too long. As other riders sped past at twice his speed, he slowed to a halt and stopped. In a humiliating scenario that every team leader dreads, he climbed off his bike and, barely able to stand, stumbled back to his team car and abandoned the Tour.

The peloton sped on without a backward glance towards the mighty Col d'Allos and the final climb to Pra Loup. Even after today there are three Alpine stages still to be endured, and tomorrow's stage alone, from Gap to St-Jean-de-Maurienne, has no less than seven climbs on the menu – including the impossibly tight hairpins of the Lacets de Montvernier.

Friday's 19th stage contains more climbs, including the final first category ascent to La Toussuire. The suffer fest climaxes on Saturday at Alpe d'Huez, when thousands of spectators — many of whom have already arrived and selected their viewing spot — will line the 21 hairpins that lead out of the valley to the ski station.

Van Garderen's abandon, after such a successful campaign for his BMC Racing team, will only fuel the attacks in Froome's wing mirrors, as his closest rivals duel for second and third place. Few of them have any hopes now of overhauling Team Sky's leader. Even so, it seems almost unthinkable – assuming he continues his spectacular form and further establishes himself as the strongest rider in the race – that any of them will be able to destabilise his hopes of final victory.